diff --git a/src/cpuexec.c b/src/cpuexec.c
index ca7401f..07db6a1 100644
--- a/src/cpuexec.c
+++ b/src/cpuexec.c
@@ -943,6 +943,34 @@ void time_fence_exit()
 	}
 }
 
+#elif defined(__EMSCRIPTEN__)
+
+// No cross-thread wait primitive is used here: this build is single-threaded
+// (see vpinball-wasm's README on why pthreads/SharedArrayBuffer are out of
+// scope), and time_fence is purely an *optional* external-clock-sync feature
+// (mirrored by Controller.TimeFence in controller.vbs) - reporting it as
+// unsupported just means the emulator paces itself on its own internal
+// timing instead of syncing to the host's clock, which is what every other
+// platform this library runs on outside of this fence do anyway.
+int time_fence_is_supported()
+{
+	return 0;
+}
+
+void time_fence_post()
+{
+}
+
+int time_fence_wait(double secs)
+{
+	(void)secs;
+	return 0;
+}
+
+void time_fence_exit()
+{
+}
+
 #else
 
 #include <semaphore.h>